Acrylic resins such as polyalkyl methacrylates, styrene resins such as ABS resin, synthetic rubbers, vinyl chloride resins and the like have been conventionally produced by so-called emulsion polymerization. Employed generally as emulsifiers in such emulsion polymerization are anionic surfactants such as alkylsulfates, alkylbenzene sulfates and polyoxyethylene alkyl ether sulfates; and nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters and PLURONIC surfactants. Synthetic resin emulsions produced by using the above-described surfactants as emulsifiers are, however, indicated to involve problems in that they tend to undergo substantial foaming due to the emulsifiers; when films are formed from the emulsions, the emulsifiers remain in a form liberated from resins in the films and cause reductions in physical properties of the films, e.g., adhesion, water resistance, weatherability and heat resistance.
In attempts to lessen these problems, numerous reactive surfactants having one or more reactive groups polymerizable with various monomers have been proposed (see, for example, Patent Documents 1-5). However, the reactive surfactants disclosed in Patent Documents 1-4 are all accompanied by problems in emulsifiability, polymerization stability, emulsion stability, post-coating water resistance and so on.
On the other hand, the reactive surfactants disclosed in Patent Documents 5 and 6 are considered to be best ones from the overall standpoint, and are good in the emulsifiability for monomers, the stability of polymer emulsions, and the water resistance of coatings and the like formed from the emulsions. They, however, involve a problem that coagulations of polymer particles abundantly occur during emulsion polymerization.    Patent Document 1: JP-B-49-046291    Patent Document 2: JP-A-62-100502    Patent Document 3: JP-A-62-011534    Patent Document 4: JP-A-63-319035    Patent Document 5: JP-A-04-053802    Patent Document 6: JP-A-62-104802